Coaxial cables are a known type of electrical cable that may be used to carry radio frequency (“RF”) signals. Coaxial cables are widely used in cable television networks, cellular communications systems and other high bandwidth applications as signals may experience less attenuation when transmitted over coaxial cable than various other types of electrical cables at the high frequencies used in such applications. FIG. 1 is a schematic perspective view of a conventional coaxial cable 10 that has been partially cut apart to reveal its internal structure. As shown in FIG. 1, the coaxial cable 10 has a center conductor 12 that is surrounded by a dielectric spacer 14. An outer conductor 16 surrounds the center conductor 12 and the dielectric spacer 14. The outer conductor 16 is typically grounded and serves as an electrical shield that reduces signal radiation (and hence signal attenuation) of the RF signal carried on the center conductor 12. Finally, a cable jacket 18 surrounds the outer conductor 16 to complete the coaxial cable 10.
A coaxial connector refers to a connector that may be attached to an end of a coaxial cable to “terminate” the coaxial cable so that the cable may be attached to an apparatus or the connector of another terminated coaxial cable. By terminating a first coaxial cable with a coaxial connector, the coaxial cable may be connected to, and subsequently disconnected from, (a) a second coaxial cable that is terminated with a “mating” coaxial connector (i.e., a coaxial connector that is designed to interface with the coaxial connector on the first coaxial cable) and (b) an apparatus that includes a mating coaxial connector. Two coaxial connectors that are connected together (“mated”) are referred to herein as a “coaxial connector junction.”
In a typical arrangement where a coaxial connector junction is used to connect a first coaxial cable to a second coaxial cable (or, alternatively, to an apparatus), a first coaxial connector is terminated onto the first coaxial cable and a second coaxial connector is terminated onto the second coaxial cable. The first coaxial connector may include a center conductor extension (often in the form of a pin or a post) that is connected to the center conductor of the first coaxial cable and an outer conductor extension (typically in the form of a connector body) that is connected to the outer conductor of the first coaxial cable. The second coaxial connector may also include a center conductor extension (often in the form of a sleeve or a contact spring) that is connected to the center conductor of the second coaxial cable and an outer conductor extension (typically in the form of a connector body) that is connected to the outer conductor of the second coaxial cable. The center conductor extension of the first coaxial connector is mated with the center conductor extension of the second coaxial connector, and the outer conductor extension of the first coaxial connector is mated with the outer conductor extension of the second coaxial connector. The first coaxial connector typically includes a threaded coupling nut and the second coaxial connector typically includes a threaded surface (or vice versa). By threading the coupling nut of the first coaxial connector onto the threaded surface of the second coaxial connector the two coaxial connectors may be drawn together into secure electro-mechanical engagement. When the first and second coaxial connectors are mated together, the coaxial connector junction is formed that electrically connects the center conductor of the first coaxial cable to the center conductor of the second coaxial cable, and that electrically connects the outer conductor of the first coaxial cable to the outer conductor of the second coaxial cable.
Passive Intermodulation Distortion (PIM) is a form of electrical interference/signal transmission degradation that may occur at interconnections, such as interconnections between two coaxial connectors, where a non-linearity is introduced into the connection, either as initially installed or due to electro-mechanical shift over time. Interconnections may shift due to mechanical stress, vibration, thermal cycling, and/or material degradation. PIM can be an important interconnection quality characteristic, as PIM generated by a single low quality interconnection may degrade the electrical performance of an entire RF system. Thus, the reduction of PIM via connector design is typically desirable. One method of reducing PIM is to use coaxial connector junctions that employ capacitive interconnections rather than galvanic interconnections.